As the Space Shuttle Atlantis blasts off for the International Space Station this weekend, NASA stands at a crucial moment: Hanging over this year's 50th anniversary of Sputnik are lingering questions for the agency amidst shifting priorities concerning manned missions to [link href='https://www.popularmechanics.com/science/air_space/4212906.html' target='_blank' link_updater_label='external_hearst']the Moon

, Mars and beyond. Popular Mechanics editor in chief Jim Meigs, executive editor David Dunbar and science editor Jennifer Bogo are on hand for another countdown in Cape Canaveral, Fla., meeting with NASA officials and following the launch minute-by-minute. Stay tuned for continuing coverage throughout the weekend...

Friday, 7:48 p.m.: Lift-off! Spectacular. Simply spectacular. It was exactly what I envisioned while daydreaming over model rockets in the 5th grade young astronauts club—only, you know, in that scenario I was on the inside of the shuttle.

What I was most unprepared for, I think, was how visceral the experience of watching a launch is. The shuttle weighs more than 4 million pounds at lift off, and more than half of that is burned as propellant in the first few minutes of flight. When the main engine fires, producing a blinding white light, a wave of sound moves through you, even at 3 miles away. The second wave occurs when the solid rocket boosters fire.

At that point, I wanted more than anything to clap my hands (I didn't, out of respect for our video—keep an eye out here for that). Instead I settled, and it's hardly settling, for admiring plumes curl behind the shuttle as it streaked 3000 mph across the sky. Good luck, guys. —Jennifer Bogo

Friday, 7:05 p.m.: Launch a No-Go? Say what? The sky is a clear, beautiful blue over Cape Canaveral, but as of right now the launch is a no-go. Unfortunately, there is inclement weather over the transatlantic runway sites in Europe; these must be clear in case the shuttle has to make an emergency landing before leaving the Earth's atmosphere.

Before we left New York, we spoke with Jeffrey Hoffman, a professor at MIT's Department of Aeronautics and Astronautics, and a five-flight veteran astronaut himself. We wanted to find out just what variables could make NASA cancel the launch. There must be clear skies and low cross winds in Florida, Hoffman says, and no thunderstorms within 10 miles of the pad. If something goes wrong and the shuttle's position in relation to the Earth has already changed, however, Western Europe needs to be clear to use as a contingency plan.

Also, we just listened to "safety precautions" announced over the PA system: A cloud of toxic vapors can form if there's an accident on the launch pad—at which point we've been advised to take shelter in the nearest air-conditioned building. Egad. —J.B.

Friday, 5:01 p.m.: The AstroBus Drive-By As launch day novices, we've been spending a lot of time hanging out with Tom Jones, a former Apollo astronaut and PM editorial advisor. Jones is here doing commentary for Fox news, and generally dispensing pieces of sage advice such as, "Listen for the whir of a security helicopter."

Thanks to this cryptic recommendation, we just experienced the closest brush we'll have with the Atlantis crew. The NASA Huey was securing the area for the "astrobus"—the silver airstream that carries the crew to the launch pad. Let's take a moment to appreciate this: The astronauts are being transported to the space shuttle by an airstream.

The bus rolls to a stop near the vehicle assembly building, and drops off Jerry Ross—a test engineer who has flown a record seven spaceflights—and Mike Greenfield—NASA's Associate Deputy Administrator for Technical Programs. Tom Jones waves at the astronauts on the other side of the tinted glass windows (three are close friends of his) and the silver door slides shut.

Now, the only people in the bus are the seven members of the crew and some support technicians—the people who strap them into the shuttle. Tonight's mission, STS-117, is the 118th shuttle flight and the 21st flight to the International Space Station. The crew will be delivering solar arrays, batteries and a 35,581-pound integrated truss segment—the heaviest element of the station to date. —J.B.

Friday, 3:30 p.m.: Launching into the Day This morning, I rolled out of bed for "space coast" eggs, served by a waitress with a "space coast" t-shirt, and tossed a magazine called "Space Coast Living" in the backseat of the rental car. I am, it seems, on the Space Coast, which is good because I am here to see the launch of the Space Shuttle Atlantis.

I arrived here last night with PM's editor-in-chief Jim Meigs and executive editor David Dunbar. Although I've edited features on whether to retire the space shuttle, and on the vehicle that will replace the shuttle after it is retired in 2010, I've never actually seen the spacecraft in person. This seems a necessary milestone in my career as the science editor at Popular Mechanics.

The press site at Kennedy Space Center sits in the shadow of the vehicle assembly building, a towering structure emblazoned with the NASA logo (if you crane your neck you can see a patch job from storm damage it sustained two summers ago). In the center of a sprawling lawn sits the count-down timer, also towering, and three miles beyond that sits the shuttle itself.

I'd have spent far more time wandering amongst the tripod forest—cameras, presumably, to join the canopy closer to blast-off—but we had to hustle to an interview with NASA administrator Mike Griffin. We spent 15 minutes asking him about the future of space exploration—not a bad way to start the day. —J.B.

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